1. Field of the Invention
The present application generally relates to suspension systems. More specifically, the present application relates to a suspension system for snow vehicles.
2. Description of the Related Art
A typical snow vehicle is designed to run on uneven snow surfaces and is thus provided with a suspension device for absorbing shocks caused by the unevenness of the snow surfaces.
Some suspension devices have a torsion spring for reducing shocks transmitted to the vehicle. An extendable shock absorber is also interposed between a body frame and the slide rail. One example of a suspension device is disclosed in Canada Patent No. 2,298,749. The suspension device with the torsion spring has a generally linear spring reaction characteristic. For example, the spring reaction increases generally linearly with the increase of the deflection of the slide rail. Thus, when a torsion spring with a relatively smaller spring constant is selected, in order to improve riding comfort, the vehicle tends to bottom-out when it encounters a relatively large bump. When a torsion spring with a relatively larger spring constant is selected, bottoming-out can be inhibited, but the suspension system is stiff and uncomfortable for the user. Ultimately, the spring reaction characteristic cannot be changed depending upon the user's preference.
In some suspension devices, one end of a torsion spring is supported on the slide rail and the other on the body. A tensioning block is disposed on the side of the slide rail to change the operation of the torsion spring. One example of a suspension device is disclosed in U.S. Pat. No. 6,354,391 B1. When the deflection of the slide rail increases beyond a prescribed amount, the spring reaction significantly increases. However, the spring reaction characteristic cannot be changed depending upon the user's preference.